You will need to set your calendar account(s) to “push” updates to your iOS device, or “fetch” updates on a regular interval.
The following steps apply to iOS 11.2.1 for iPhone. If these instructions don’t work for you and you’re running the same or a later version, please edit or comment as appropriate.
1. Open your Settings app.
2. Scroll to “Accounts & Passwords.” Don’t select “Calendars.” (Not intuitive, I know.)
- In the new screen, scroll all the way down to “Fetch New Data.” Don’t choose “iCloud” or any other account yet. (Still not intuitive, right?!)
- In this screen, choose the desired account for the calendar(s) that you want to affect and set it to “Push” or “Fetch.” You may also want to turn on/off “Push” at the top, depending on your needs. In this case, I have “Push” turned on at the top and set iCloud to take advantage of the option. All others are set to manually check the accounts when I run the app.